For the treatment of a proximal femur fracture (subtrochanteric or intertrochanteric fracture or femoral neck fracture) with an implant, an intramedullary nail is usually introduced into the femur bone and the femur head is fixed via a femoral neck screw journaled in the proximal section of the medullary nail. The femoral neck screw is guided for this purpose through a slanted bore in the proximal section of the medullary nail and is anchored in the spongiosa of the femoral head by screwing in. In this context, proximal means closer to the body or to the heart of a patient, whereas distal means the opposite.
Femoral neck fractures are furthermore frequently treated in that a plate comprising a sleeve facing in the direction of the femoral neck is fixed laterally to the femur, with the sleeve coming to lie medially in the femur. A femoral neck screw is slidingly guided in the sleeve and its proximal end is anchored in the femoral head.
To achieve a stable anchorage of the femoral neck screw, attempts are in particular made to achieve a stable anchorage of the screw in the femoral head, which also offers security against rotation, by a special embodiment of the thread of the femoral neck screw. It has also already been proposed to introduce both a screw and a pin for security against rotation into the femoral head in parallel. The anchorage of a femoral neck screw, above all in osteoporotic bones, cannot be effected without difficulties.
An osteosynthetic screw also has to be anchored with low stability in bone tissue on other indications for fracture treatment; the proximal humerus could be named by way of example. Furthermore, explanation of the implant after healing has taken place should, where possible, also be possible with implants for fracture treatment, which brings about an additional constraint in comparison with prosthetic applications.
A prosthesis for filling a passage in the femoral head core is known from WO 96/39974. This prosthesis has a porous filling part for the filling of the passage. It is provided to be connected to the bone tissue. Necrotic bone substance is thus reinforced.
A tubular implant is described in US2003/0045885 which can be anchored in the bone in a self-tapping manner, for example. The surface of this implant can be porous to integrate better into the bone tissue. The implant serves for the reinforcement of osteoporotic bone tissue in the area of the femoral neck.
An intramedullary implant for a hip joint prosthesis can be seen from U.S. Pat. No. 3,852,045 which has a firm and structurally loadable central region as well as firmly connected porous regions at each axial end.